The objective of the proposed work is to develop technology which results in probes ultrasound with performance at or near the level of probes designed for diagnostic imaging but with the increased efficiency and power handling capability which is necessary for some applications, such as acoustic radiation force impulse (ARFI) imaging and combined imaging / HIFU therapy. Probes with high bandwidth, sensitivity, and efficiency will enable ARFI to operate in real time and will improve the image guidance for HIFU applications. Development of multilayer multirow array technology will ultimately lead to better elevation focusing capability in both diagnostic and therapy modes, and open the possibility of electrically matched array elements without the need for a transformer. Thus resolution can be improved for imaging, and therapy devices can be easily focused at multiple depths for treatment of both near-surface and deep-lying ailments with a single device. The specific aims of Phase I are as follows. Experimentally validate through thermocouple measurements the relative power dissipation of probe components, such as the backing, piezoceramic, and lens materials. Compare the power dissipation and efficiency of probes designed for diagnostic imaging with that of probes designed for increased power handling capability using low loss piezoceramic and modified acoustic designs. Evaluate the properties of low loss piezoceramic multilayers by fabricating prototypes with an established process. Establish the feasibility of applying stacked multilayer technology to multirow arrays by extending established processes to individual multilayers with small elevation dimensions and to selectively plated full-elevation plates. In cooperation with researchers active in the field, determine probe configurations and performance specifications for high resolution high power arrays which can benefit from the technology developed in this program.